Flashcards in Endocrine System Deck (78)
General characteristics of hormones:
-Specific rates and rhythms of secretions (diurnal, pulsatile, and cyclic)
-Feedback systems (positive-self amplifying, negative-inhibitory)
-Target cells with appropriate receptors
-Liver inactivates hormones; renal excretion
Hormones are released:
-In response to an alteration
-To maintain a regulated level (homeostatic balance)
Hormones are regulated by:
Chemical (ie-blood sugar-insulin, Ca levels-calcitonin and PTH)
Hormonal (hormone from one endocrine gland controlling another gland. ie-TSH to T4 release)
Neural factors (ie- release of epi from adrenal medulla and ADH and oxytocin release stimulated by glutamate and inhibited by GABA)
Hormones released by Pituitary/Hypothalmus:
Intermediate- MSH (melanocyte stimulating hormone)
Posterior- ADH, Oxytocin (made in hypothalmus, stored in posterior pit)
Hormones released by the Thyroid:
Thyroxine, T3, T4
What does FLATPiG consist of?
Anterior Pit hormones: FSH, LH, ACTH, TSH, Prolactin, and GH
Hormones released by the Parathyroid:
Hormones released by the Adrenal Cortex:
Weak Androgens (ie-DHEA)
Hormones released by the Adrenal Medulla:
Hormones released by the Pancreas:
Hormones released by the Ovary:
Hormones released by the Testis:
What is the most common type of feedback system regulating endocrine function?
What is up-regulation?
An increase in receptor number causes an increase in hormone effect d/t ability to bind to more receptors.
What is down-regulation?
A decrease in receptor number causing a decrease in hormone effect.
What is the purpose of up and down-regulation?
Regulation of target cell sensitivity. By altering the number of receptors on target cell for a particular hormone
How do water soluble hormones enter target cell?
Water soluble hormones circulate in free/unbound forms. They cannot diffuse across the plasma membrane. Require receptor on membrane and use a second messenger.
How do lipid soluble hormones enter a target cell?
Lipid soluble hormones circulate bound to a carrier (usually a globulin). They are able to easily diffuse across the membrane and target intracellular receptors (cytosolic or nuclear) and activate RNA polymerase or DNA transcription and translation =synthesize proteins
Explain water soluble hormone mechanism of action.
-First messenger (bind to receptor)
-Second messenger molecules (Ca, cAMP, or cGMP)
What are some examples of water soluble hormones?
LH, FSH, insulin, epinephrine, norepinephrine, GH, TSH
What are some examples of lipid soluble hormones?
Steroids- androgen, estrogen, progestin, glucocorticoids, mineralcorticoids, cortisol, calcitrol
T3 and T4
What is the hypophyseal portal system?
Neurons in the hypothalmus secrete releasing hormones into veins that carry the releasing hormones directly to the vessels of the anterior pituitary, thus bypassing the normal circulatory route.
Where are the pituitary glands located?
Below the hypothalmus in the sella turcica at the base of the skull.
What connects the hypothalmus to the posterior pituitary?
Pituitary stalk. Neurons within which require an action potential
What connects the hypothalmus to the anterior pituitary?
When is ADH(vasopressin) released by the posterior pituitary?
Released in response to altered serum osmolality and hypotension and causes water retention by increasing water reabsorption by the renal collecting duct.
When is oxytocin released by the posterior pituitary?
Released during sex, childbirth, and breastfeeding. Causes uterine and milk duct contractions.
What is the three tiered axis of the hypothalmic-qpituitary endocrine system?
1. Hypothalmus (release or inhibit hormones-often in a pulsatile rhythm)
2. Anterior Pituitary Hormones
3. Target organ hormones
GH and the anterior pituitary gland?
-Controlled by hypothalmic release of GHRH and growth inhibiting hormone (somatostatin). Ant pit release small pulsatile amount of GH each day.
-Liver is the major target. Affects liver metabolism and stimulates production of insulin-like growth factor 1
-GH affects metabolic processes. Ie- increase rate of protein synthesis and slow carb utilization
-Hypoglycemia and increased concentration of amino acids in blood stimulates GH release